Slow Reaction Rate Research Articles

Inhibition of chlorinated byproducts formation by boron-doped rGO electrodes during electrooxidation of trace organic contaminants

To minimize toxic inorganic chlorinated byproducts formation by anodic oxidation of chloride containing water, an electrode was fabricated by coating boron-doped reduced graphene oxide (BDrGO) on carbon paper. The BDrGO electrode only converted 0.03 to 0.4 % of the initial chloride (5–25 mM) to byproducts across a wide pH range (3−10), which is approximately two orders of magnitude lower than other commonly used anodes. The mechanism for inhibiting chlorinated byproducts was attributed to the higher overpotential for the chlorine evolution reaction on the BDrGO electrode and the slower reaction rates (< 2 × 10−11 M s–1) of pathways responsible for chlorinated byproducts formation. The BDrGO electrode was capable of oxidizing contaminants, with oxidation pathways predominated by chlorine radicals (e.g., ClO•, Cl•, Cl2•–) (> 50 %). During electrolysis of authentic surface water, the BDrGO electrode transformed trace organic contaminants (> 90 %) without producing unacceptable levels of chlorinated byproducts.

Nano-etching of carbon nanofiber surface and subsequent Fe–N–C thin film coating for enhancement of oxygen evolution reaction

The oxygen evolution reaction (OER) is involved in many electrical–chemical energy conversion systems; however, the slow reaction rate of the OER leads to a high overpotential (η) and low energy efficiency. Recently, an extremely low-η OER phenomenon was observed at a carbonaceous Fe–N-doped thin film with enriched step edges on highly oriented pyrolytic graphite and the carbon fiber surface in an alkaline electrolyte, although the activity was limited. In this study, multi-walled carbon nanotubes (MWCNTs) were used as substrates to utilize their high specific surface areas to develop an active OER catalyst. Nanoscale etching of the MWCNT surface was performed by Fe3O4 nanoparticle loading and subsequent heat treatment in an inert atmosphere, followed by acid washing. Afterwards, a carbonaceous thin film containing Fe and N was coated on the surface via sublimation, deposition, and pyrolysis of Fe phthalocyanine (Pc). A roughened surface was observed for the FePc-derived thin film coated on the nano-etched MWCNT, in contrast to the smooth surface observed for the film coated on the MWCNT without nano-etching. The combination of the nano-etching and the thin-film coating enhanced the OER, which was analyzed by parallel Tafel processes.

Drastically Accelerated Radical Recombination Kinetics of a Hexaarylbiimidazole Derivative.

More than 60 years have passed since the discovery of hexaarylbiimidazole (HABI), which exhibits a characteristic photochromism that produces colored lophyl radicals through a radical dissociation reaction induced by light irradiation and reverts to its original state through a radical recombination reaction in the dark. Lophyl radicals are relatively stable among organic radicals, have low reactivity with oxygen, and have a very slow radical recombination reaction rate. HABI has been used industrially as a photoinitiator to date. However, the guidelines for molecular design to accelerate the thermal reverse reaction of HABI are still unknown and remain a challenge. We found that suppressing the rotation of the phenyl groups attached to the 4- and 5-positions of the imidazole ring of HABI is effective in accelerating the radical recombination reaction. The simple molecular design strategy to accelerate the thermal reverse reaction of HABI is expected to improve the performance of photoinitiators and photoresponsive materials that utilize HABI as a photoresponsive unit.

Effect of steel-refractory reactions on inclusion modification in lanthanum-, cerium-, and yttrium-added steels

The reactions of rare earth elements (REEs) with refractory materials significantly affect their effective concentrations and inclusion modifications in molten steel. This study investigated the influence of steel-refractory reactions on the modification of inclusions in lanthanum-, cerium-, and yttrium-added steels utilizing three types of commonly used crucibles as smelting vessels. Steel-refractory reactions were found to strongly affect inclusions with different outcomes for smelting in MgO, Al2O3, and MgO·Al2O3 crucibles. The RE-crucible reactions affected the evolution and size of inclusions in molten steel by influencing the content of [Mg] and [Al]. The RE-MgO crucible reactions increased [Mg] content, leading to more MgO inclusions and a smaller average size. The RE-Al2O3 crucible reactions increased [Al] content, resulting in more REAlO3 inclusions and a bigger average size. The reactions of La, Ce, and Y with MgO·Al2O3 crucibles had varying effects on the evolution of inclusions. La and Ce selectively eroded the crucible, mostly reacting with the Al2O3 component and generating REAlO3 inclusions. In contrast, the slow reaction rate of Y with the crucible and the formation of the dense Y2O3 layer at the steel/crucible interface made it react almost simultaneously with both MgO and Al2O3 components, and the modification of inclusions was dominated by [Mg] rather than [Al]. The above conclusions provided more information on how the reactions between rare earth elements and refractory materials affected inclusions in rare earth steels during smelting. They also enriched the theory of inclusion control in steel and offered new controlling strategies.

Fabrication of a Cancer Cell Aggregate Culture Device That Facilitates Observations of Nutrient and Oxygen Gradients.

Three-dimensional cell culture spheroids are commonly used for drug evaluation studies because they can produce large quantities of homogeneous cell aggregates. As the spheroids grow, nutrients supplied from outer spheroid regions render the inner spheroid areas hypoxic and hyponutrient, which makes them unobservable through confocal microscopy. In this study, we fabricated a cancer cell aggregate culture device that facilitates the observation of nutrient and oxygen gradients. An alginate gel fiber was created in the cell culture chamber to ensure a flow path for supplying the culture medium. A gradient of nutrients and oxygen was generated by positioning the flow channel close to the edge of the chamber. We devised a fabrication method that uses calcium carbonate as a source of Ca2+ for the gelation of sodium alginate, which has a slow reaction rate. We then cultured a spheroid of HCT116 cells, which were derived from human colorectal carcinoma using a fluorescent ubiquitination-based cell cycle indicator. Fluorescence observation suggested the formation of a hypoxic and hyponutrient region within an area approximately 500 µm away from the alginate gel fiber. This indicates the development of a cancer cell aggregate culture device that enables the observation of different nutrition and oxygen states.

Wurtzite CdS ratio tunability on α-Fe2O3/CdS synergistic heterostructure for enhanced UV-induced photocatalytic decomposition of rhodamine 6G dye pollutant

Hematite α-Fe2O3 exhibits a slow catalytic reaction rate and low performance in aqueous pollutant decomposition. In this work, α-Fe2O3/CdS binary heterostructure composites were created by introducing different ratios of wurtzite CdS into α-Fe2O3 within 0–100 wt% via precipitation and impregnation methods. The photocatalytic performance of α-Fe2O3/CdS was enhanced for the decomposition of aqueous rhodamine 6G (R6G) dye under ultraviolet (UV) irradiation. SEM images reveal that higher CdS loading results in increased interfacial contact between rod-like CdS and spherical-shaped α-Fe2O3. XRD and FTIR results confirm the coexistence of rhombohedral α-Fe2O3 and hexagonal CdS phases, with peak strength proportional to the ratio of component loading, as the respective elements were verified through EDX analysis. The UV-Vis spectroscopic analysis exhibits an enhancement in optical absorption and band gap broadening as the CdS loading rises. α-Fe2O3/CdS with increased CdS loading exhibits faster and more efficient R6G degradation under UV exposure, as evidenced by greater rate constants and degradation efficiency, with optimal CdS loading of 90 wt% achieving a maximum efficiency of 79.14%. The present heterostructure could be employed in future wastewater remediation for effective removal of organic dye pollutants, further promoting clean water preservation for global environmental sustainability.

Intelligent near-infrared light-activatable DNA machine with DNA wire nano-scaffold-integrated fast domino-like driving amplification for high-performance imaging in live biological samples

While there is significant potential for DNA machine-built enzyme-free fluorescence biosensors in the imaging analysis of live biological samples, they persist certain shortcomings. These encompass a deficiency of signal enrichment within a singular interface, uncontrolled premature activation during bio-delivery, and a slow reaction rate due to free nucleic acid collisions. In this contribution, we are committed to resolving the above challenges. Firstly, a single-interface-integrated domino-like driving amplification is constructed. In this conception, a specific target acts as the domino promotor (namely the energy source), initiating a cascading chain reaction that grafts onto a singular interface. Next, an 808 nm near-infrared (NIR) light-excited up-converting luminescence-induced light-activatable biosensing technique is introduced. By locking the target-specific identification segment with a photo-cleavage connector, the up-converted ultraviolet emission can activate target binding in a completely controlled manner. Moreover, a fast reaction rate is achieved by confining nucleic acid collisions within the surface of a DNA wire nano-scaffold, leading to a substantial enhancement in local contact concentration (30.8-fold increase, alongside a 15 times elevation in rate). When a non-coding microRNA (miRNA-221) is positioned as the model low-abundance target for proof-of-concept validation, our intelligent DNA machine demonstrates ultra-high sensitivity (with a limit of detection down to 62.65 fM) and good specificity for this hepatic malignant tumor-associated biomarker in solution detection. Going further, it is worth highlighting that the biosensing system can be employed to carry out high-performance imaging analysis in live bio-samples (ranging from the cellular level to the nude mouse body), thereby propelling the field of DNA machines in disease diagnosis.

Unveiling the hydroesterification of 1,3-butadiene with carbonyl cobalt ionic liquids: Facilitation of cationic protonic hydrogen for active species formation

The 1,3-butadiene hydroesterification products, such as methyl pentenoate and dimethyl adipate, play a significant role in the production of nylon, plasticizers, and pharmaceutical intermediates. However, due to its unique π-π conjugated system, slow reaction rate, and difficulties in controlling regioselectivity, butadiene presents itself as an incredibly challenging substrate. The development of efficient and low-cost catalysts has gained substantial attention in both theoretical studies and industrial applications due to the high cost or extremely high pressure requirements. In this study, carbonyl cobalt ionic liquids were innovatively employed as catalysts to facilitate the synthesis of monoesters from hydroesterification of butadiene under mild conditions. A series of carbonyl cobalt ionic liquids with different cations were prepared and characterized for their structural properties using IR, ESI, IC, and DFT calculations. The yield of methyl pentenoate was comparable to that of Co2CO8 at 400 bar, and the catalysts exhibited high selectivity to methyl 3-pentenoates (>95 %), establishing a stable, efficient, and low-cost catalytic system. The experiments revealed that the type of the cation in ionic liquids remarkably influence their catalytic performance. Electrostatic potential calculations further confirmed that this performance is tightly related to the dissociation and migration behaviors of protons, leading to the proposal of a screening method for ionic liquids. In this paper, we further calculated the qualitative reaction kinetics and proposed a reaction mechanism in conjunction with previous studies. The reaction is hypothesized to begin with the formation of the active species HCo(CO)4 by proton exchange of [HX]+[Co(CO)4]−, in line with our experimental findings and theoretical calculations. This study presents an innovative approach to overcome the challenges associated with butadiene hydroesterification and paves the way for the development of more efficient and cost-effective catalytic systems.

Application Of Advanced Oxidation Process Based on Ozone in Water Treatment

Wastewater treatment is an effective way to address water scarcity. Advanced oxidation processes (AOPs) are a wastewater treatment technology that is currently attracting a lot of attention, and it is a technology that uses physical or chemical pathways such as ozone, ultraviolet light, and the Fenton reaction to generate free radicals and then treats pathogens and organic pollutants by oxidation of the free radicals.Ozone is very strong oxidising agent and it has a powerful ability to break down wide range of organic and inorganic pollutants. However its usage in the wastewater treatment is still not very popular due to several drawbacks it posses, as it not possible to achieve the goal of wastewater treatment by ozone alone due to its mass transfer limitations, slow reaction rates, non specific for certain under low reaction rates pollutants select,may costs relatively higher thanother treatment processes etc. By combining ozone with H2O2, UV light, and catalysts, the efficiency of the wastewater treatment process will be increased because it will help make more hydroxyl radicals. This review discusses various ozone-based AOPs such as ozone/UV, ozone/hydrogen peroxide, and catalytic ozonation, focusing on their mechanisms and applications in wastewater treatment.

The intermediate valence state Mo5+ in Fe doping La2(MoO4)3 boosting electrochemical nitrogen reduction

NH3 is considered as an ideal fuel for fuel cells to achieve zero carbon emissions due to its high energy density (at liquefaction) and carbon-free properties. The zero-carbon clean electrocatalytic nitrogen reduction reaction (NRR) is one of the alternative routes for NH3 synthesis. The efficiency of NRR is restricted by the high stability of N N and the slow reaction rate. In this study, La2(MoO4)3 (LaMo), and x%Fe doping-LaMo (x = 3, 5, 7, and 10) are synthesized via a hydrothermal method. The strong electron-donating ability of Fe converts a part of Mo6+ to Mo5+ and Mo4+ improving the electronic environment. The presence of Mo5+, an intermediate valence state, facilitates the oxidation and reduction reactions and establishes rapid electron transport channels. The electron transport of Mo6+↔e−Mo5+ is easier than Mo6+↔2e−Mo4+. Furthermore, the Mo5+ activates N2 and enhances N2 adsorption, boosting the NRR performance. Importantly, the content of Mo5+ exhibits a positive correlation with NH3 yield rate (R2 = 0.89), and Faradaic efficiency (FE, R2 = 0.95). Consequently, the 5%Fe–LaMo exhibits the highest Mo5+ percentage (75.9 %) and NRR performance (NH3 yield rate:30.4 μg h−1 mgcat−1, FE: 3.6 %). Thus, this study proposes a method to enhance the NRR performance by element doping with strong electron-donating ability to regulate the Mo5+ percentage.

Synthesis and electrochemical investigation of Cu@FeLn (Eu, Sm, and Gd)-N-C composites for energy conversion and storage applications

The slow reaction rates observed in the Oxygen Reduction Reaction (ORR) pose a significant obstacle in advancing fuel cell technology. Consequently, ORR plays a pivotal role in determining the operational efficiency of fuel cell and energy storage systems. Accordingly, the synthesis of a cathodic electrocatalyst with high efficiency has become an attractive topic for researchers. In this empirical study, three trimetallic electrocatalysts are synthesized and electrochemically appraised. By introducing three lanthanides, namely Gadolinium (Gd), Samarium (Sm), and Europium (Eu), into CuFeZIF-8, new composites successfully are synthesized as Cu@FeLn (Eu, Sm, and Gd)-N-C. These functional materials find application in the context of the ORR and supercapacitor technologies. In order to enhance stability, control surface area, and prevent agglomeration during high-temperature pyrolysis, the silicon cover protection technique is employed. The primary objective in this investigation is to assess the influence of mSiO2 coating on the electrochemical parameters of these electrocatalysts. To characterize the fabricated samples, seven characterization tests are utilized. Electrochemical measurements are conducted employing a three-electrode cell configuration within an alkaline environment. The results illustrated that the Cu@FeGd-N-C sample, with an onset potential of −0.043 V vs. Ag/AgCl, exhibited the best ORR performance. Also, the electron transfer number of Cu@FeSm-N-C was computed as 3.56. The half-wave potentials of Cu@FeSm-N-C, Cu@FeEu-N-C, and Cu@FeGd-N-C were found to be −0.34, −0.23, and −0.18 V vs. Ag/AgCl, respectively. A less negative half-wave potential typically suggests superior performance, signifying a lower overpotential requirement for the ORR process. The specific capacitance for Cu@FeGd-N-C electrode at 1 A/g was determined as 144.4 F g−1. The inclusion of lanthanides, Fe, and Cu into ZIF-8 is observed to notably improve both catalytic activity and electron transfer. Also, the outcomes showed that mesoporous silica-protected pyrolysis could be a useful strategy for improving the efficiency of energy conversion and energy storage equipment.

Environmental Markers of Plastics and Microplastics.

The slow reaction rates to chemical and photochemical degradation are well-known properties of plastics. However, large plastic surfaces exposed to environmental conditions release particles and compounds that affect ecosystems and human health. The aim of this work was to identify compounds associated with the degradation of polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC) microplastics (markers) on silica and sand and evaluate their use to screen microplastics on natural sand. Products were identified by using targeted and untargeted LC-HRMS analysis. All polymers underwent chemical oxidation on silica. PE released dicarboxylic acids (HO2C-(CH2)n-CO2H (n = 4-30), while PS released cis/trans-chalcone, trans-dypnone, 3-phenylpropiophenone, and dibenzoylmethane. PVC released dicarboxylic acids and aromatic compounds. Upon irradiation, PE was stable while PS released the same compounds as under chemical oxidation but at lower yields. Under the above condition, PVC generated HO2C-[CH2-CHCl]n-CH2-CO2H and HO2C-[CH2-CHCl]n-CO2H (n = 2-19) dicarboxylic acids. The same products were detected on sand but at a lower concentration than on silica due to better retention within the pores. Detection of markers of PE and PS on natural sand allowed us to screen microplastics by following a targeted analysis. Markers of PVC were not detected before or after thermal/photo-oxidation due to the low release of compounds and limitations associated with surface exposure/penetration of radiation.

Frontal polymerisation of acrylic acid tuned by micellar aggregates in a deep eutectic solvent

A frontal polymerisation (FP) is obtained when a polymerisation creates a spatial front of the reaction. Because of the heat of the reaction associated, a temperature spatial front is also observed. In this paper, the usual chain polymerisation of acrylic acid (AA) is studied when the monomer forms a deep eutectic solvent (DES), i.e. a liquid similar to an ionic liquid. In this DES, AA behaves as a hydrogen donor and ethylammonium chloride as a hydrogen acceptor. The use of a DES is convenient as an effective polymerisation media because the heat of the reaction can be controlled. We study the rate and the heat of polymerisation during the formation of a front using micellar structures where a bifunctional peroxide hydrophobic initiator, abbreviated Luperox, dissolves successfully. Our experiments follow the FP using infrared images and rheology. We found that micellar aggregates of different sizes are interesting modulators of the polymerisation rate and heat of the reaction. Our results show that smaller aggregates produce higher rates of reaction with a decoupled increment of temperature; in contrast to what is observed with bigger aggregates: a slow reaction rate with a coupled moderate heat of reaction.

RuBisCO activity assays: a simplified biochemical redox approach for in vitro quantification and an RNA sensor approach for in vivo monitoring

BackgroundRibulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is the most abundant soluble protein in nature. Extensive studies have been conducted for improving its activity in photosynthesis through approaches like protein engineering. Concurrently, multiple biochemical and radiolabeling assays have been developed for determining its activity. Although these existing assays yield reliable results, they require addition of multiple external components, rendering them less convenient and expensive. Therefore, in this study, we have developed two relatively cheaper, convenient, and easily reproducible assays for quantitative and qualitative estimation of RuBisCO activity.ResultsWe simplified a contemporary NADH based spectrophotometric RuBisCO assay by using cyanobacterial cell lysate as the source for Calvin cycle enzymes. We analyzed the influence of inorganic carbon substrates, CO2 and NaHCO3, and varying protein concentrations on RuBisCO activity. Ribulose-1,5-bisphosphate (RuBP) consumption rates for the cultures grown under 5% CO2 were 5–7 times higher than the ones grown with 20 mM NaHCO3, at different protein concentrations. The difference could be due to the impaired activity of carbonic anhydrase in the cell lysate, which is required for the conversion of HCO3− to CO2. The highest RuBisCO activity of 2.13 nmol of NAD+/ µg of Chl-a/ min was observed with 50 µg of protein and 5% CO2. Additionally, we developed a novel RNA-sensor based fluorescence assay that is based on the principle of tracking the kinetics of ATP hydrolysis to ADP during the conversion of 3-phosphoglycerate (3-PG) to 1,3-bisphosphoglycerate (1,3-BPG) in the Calvin cycle. Under in vitro conditions, the fluorometric assay exhibited ~ 3.4-fold slower reaction rate (0.37 min−1) than the biochemical assay when using 5% CO2. We also confirmed the in vivo application of this assay, where increase in the fluorescence was observed with the recombinant strain of Synechocystis sp. PCC 6803 (SSL142) expressing the ADP-specific RNA sensor, compared to the WT. In addition, SSL142 exhibited three-fold higher fluorescence when supplemented with 20 mM NaHCO3 as compared to the cells that were grown without NaHCO3 supplementation.ConclusionsOverall, we have developed a simplified biochemical assay for monitoring RuBisCO activity and demonstrated that it can provide reliable results as compared to the prior literature. Furthermore, the biochemical assay using 5% CO2 (100% relative activity) provided faster RuBP consumption rate compared to the biochemical assay utilizing 20 mM NaHCO3 (30.70% relative activity) and the in vitro fluorometric assay using 5% CO2 (29.64% relative activity). Therefore, the absorbance-based biochemical assay using 5% CO2 or higher would be suitable for in vitro quantification of the RuBisCO activity. On the other hand, the RNA-sensor based in vivo fluorometric assay can be applied for qualitative analysis and be used for high-throughput screening of RuBisCO variants. As RuBisCO is an enzyme shared amongst all the photoautotrophs, the assays developed in this study can easily be extended for analyzing the RuBisCO activities even in microalgae and higher plants.

Schottky-assisted S-scheme heterojunction photocatalyst CdS/Pt@NU-1000 for efficient visible-light-driven H2 evolution

Coupling metal-organic frameworks (MOFs) with inorganic semiconductors to construct S-scheme heterojunction photocatalysts is an effective way to facilitate photocarriers transfer and separation, as well as enhance redox ability for photocatalytic water-splitting into H2. However, the poor electrical conductivity of MOFs, fast recombination of photogenerated electron-hole pairs, and slow surface redox reaction rates on photocatalysts lead to inefficient consumption of all charge carriers thus impeding further improvement of photocatalytic activity. Thus, optimizing the separation, transfer, and utilization efficiencies of interfacial charge carriers in MOFs-based S-scheme heterojunction may pave the way for achieving excellent photocatalytic activity. Herein, a novel Schottky-assisted S-scheme heterojunction photocatalyst CdS/Pt@NU-1000 was prepared by the combination of Pt-embedded NU-1000 with CdS. The optimized photocatalyst CdS/0.7Pt@NU-1000 exhibits the highest visible-light-driven H2 evolution rate with 3.604 mmol g–1 h–1, which is 12.7 and 18.8 folds of that for single CdS and NU-1000, respectively. The splendid photocatalytic performance benefited from the broadened light absorption, and the synergistic effect of the formed Schottky junction and S-scheme heterojunction. Furthermore, the formation of the S-scheme system was validated by density functional theory (DFT) calculations, in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS), and electron paramagnetic resonance (EPR) test. This work can provide some guidance for the design of efficient heterojunction photocatalysts by optimizing interfacial charge transfer.

Polyurethane Foam Chemical Recycling: Fast Acidolysis with Maleic Acid and Full Recovery of Polyol.

Chemical recycling of polyurethane (PU) waste is essential to displace the need for virgin polyol production and enable sustainable PU production. Currently, less than 20% of PU waste is downcycled through rebinding to lower value products than the original PU. Chemical recycling of PU waste often requires significant input of materials like solvents and slow reaction rates. Here, we report the fast (<10 min) and solvent-free acidolysis of a model toluene diisocyanate (TDI)-based flexible polyurethane foam (PUF) at <200 °C using maleic acid (MA) with a recovery of recycled polyol (repolyol) in 95% isolated yield. After workup (hydrolysis of repolyl ester and separations), the repolyol exhibits favorable physical properties that are comparable to the virgin polyol; these include 54.1 mg KOH/g OH number and 624 cSt viscosity. Overall, 80% by weight of the input PUF is isolated into two clean-cut fractions containing the repolyol and toluene diamine (TDA). Finally, end-of-life (EOL) mattress PUF waste is recycled successfully with high recovery of repolyol using MA acidolysis. The solvent-free and fast acidolysis with MA demonstrated in this work with both model and EOL PUF provides a potential pathway for sustainable and closed-loop PU production.

Ru Regulated Electronic Structure of PdxCuy Nanosheets for Efficient Hydrogen Evolution Reaction in Wide pH Range.

The development of highly effective catalysts for hydrogen evolution reaction (HER) in a wide pH range is crucial for the sustainable utilization of green energy utilization, while the slow kinetic reaction rate severely hinders the progress of HER. Herein, the reaction kinetic issue is solved by adjusting the electronic structure of the Ru/PdxCuy catalysts. The champion catalyst displays a remarkable performance for HER with the ultralow overpotential (27, 28, and 97mV) in 1.0m KOH, 0.5m H2SO4, and 1.0m PBS at 10mA cm-2 and high the mass activity (3036 A g-1), respectively, superior to those of commercial Pt/C benchmarks and most of reported electrocatalysts, mainly due to its low reaction activation energy. Density functional theory (DFT) calculations indicate that Ru doping contributes an electron-deficient 3d band, which promotes water adsorption. Additionally, this also leads to an upward shift of the d-band center of Pd and a downward shift of the d-band center of Cu, further optimizing the adsorption/dissociation of H2O and H*. Results from this work may provide an insight into the design and synthesis of high-performance pH-universal HER electrocatalysts.

Weathering Incongruence in Mountainous Mediterranean Climates Recorded by Stream Lithium Isotope Ratios

AbstractLithium isotope ratios (δ7Li) of rivers are increasingly serving as a diagnostic of the balance between chemical and physical weathering contributions to overall landscape denudation rates. Here, we show that intermediate weathering intensities and highly enriched stream δ7Li values typically associated with lowland floodplains can also describe small upland watersheds subject to cool, wet climates. This behavior is revealed by stream δ7Li between +22.4 and +23.5‰ within a Critical Zone observatory located in the Cévennes region of southern France, where dilute stream solute concentrations and significant atmospheric deposition otherwise mask evidence of incongruence. The water‐rock reaction pathways underlying this behavior are quantified through a multicomponent, isotope‐enabled reactive transport model. Using geochemical characterization of soil profiles, bedrock, and long‐term stream samples as constraints, we evolve the simulation from an initially unweathered granite to a steady state weathering profile which reflects the balance between (a) fluid infiltration and drainage and (b) bedrock uplift and soil erosion. Enriched stream δ7Li occurs because Li is strongly incorporated into actively precipitating secondary clay phases beyond what prior laboratory experiments have suggested. Chemical weathering incongruence is maintained despite relatively slow reaction rates and moderate clay accumulation due to a combination of two factors. First, reactive primary mineral phases persist across the weathering profile and effectively “shield” the secondary clays from resolubilization due to their greater solubility. Second, the clays accumulating in the near‐surface profile are relatively mature weathering byproducts. These factors promote characteristically low total dissolved solute export from the catchment despite significant input of exogenous dust.

ProPhos: A Ligand for Promoting Nickel-Catalyzed Suzuki-Miyaura Coupling Inspired by Mechanistic Insights into Transmetalation.

Nickel-catalyzed Suzuki-Miyaura coupling (Ni-SMC) offers the potential to reduce the cost of pharmaceutical process synthesis. However, its application has been restricted by challenges such as slow reaction rates, high catalyst loading, and a limited scope of heterocycles. Despite recent investigations, the mechanism of transmetalation in Ni-SMC, often viewed as the turnover-limiting step, remains insufficiently understood. We elucidate the "Ni-oxo" transmetalation pathway, applying PPh2Me as the ligand, and identify the formation of a nickel-oxo intermediate as the turnover-limiting step. Building on this insight, we develop a scaffolding ligand, ProPhos, featuring a pendant hydroxyl group connected to the phosphine via a linker. The design preorganizes both the nucleophile and the nickel catalyst, thereby facilitating transmetalation. This catalyst exhibits fast kinetics and robust activity across a wide range of heteroarenes, with a catalyst loading of 0.5-3 mol %. For arene substrates, the catalyst loading can be further reduced to 0.1 mol %.

Hybrid Electrolyte Based on PEO and Ionic Liquid with In Situ Produced and Dispersed Silica for Sustainable Solid-State Battery

This work introduces the synthesis of hybrid polymer electrolytes based on polyethylene oxide (PEO) and electrolyte solution bis(trifluoromethane)sulfonimide lithium salt/ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (LiTFSI/EMIMTFSI) with in situ produced and dispersed silica particles by the sol–gel method. Conventional preparation of solid polymer electrolytes was followed by desolvation of lithium salt in a polymer matrix of PEO, which, in some cases, additionally contains plasticizers. This one-pot synthesis is an alternative route for fabricating a solid polymer electrolyte for solid-state batteries. The presence of TFSI- reduces the crystallinity of the PEO matrix (plasticizing effect), increases the dissociation and solubility of LiTFSI in the PEO matrix because of a highly delocalized charge distribution, and reveals excellent thermal, chemical, and electrochemical stability. Tetraethylorthosilicate (TEOS) was chosen due to the slow reaction rate, with the addition of (3-glycidyoxypropyl)trimethoxysilane (GLYMO), which contributes to the formation of a silica network. FTIR studies confirmed the interactions between the silica, the polymer salt, and EMIMTFSI. Impedance spectroscopy measurements were performed in a wide range of temperatures from 25 to 70 °C. The electrochemical performance was explored by assembling electrolytes in LiCoO2 (LCO), NMC(811), and LiFePO4 (LFP) coin half-cells. The HPEf15 shows a discharge capacity of 143 mA/g for NMC(811) at 0.1 C, 134 mA/g for LCO, and 139 mA/g for LFP half-cells at 0.1 C and 55 °C. The LFP half-cell with a discharge capacity of 135 mA/g at 0.1 C (safety potential range of 2.8 to 3.8) obtained a cyclability of 97.5% at 55 °C after 100 cycles. Such a type of electrolyte with high safety and good electrochemical performance provides a potential approach for developing a safer lithium-ion battery.